A little back story. My truck is at 110K miles, I bought it 11 monhts ago at 97K miles, and the only thing on the Oasis was a new EGR Valve at 92K miles. Within 100 miles of the purchase I threw the wrench light, and the oil cooler was replaced, but I was reassured the EGR cooler was fine.

Jump to January or February of this year and around 101K miles, I did my coolant flush and I received my first p0401 while driving my truck around for the 90 minute warm up period. I had to put Ford Gold Coolant back in as I dumped all my coolant at the start of my coolant flush and after I had talked to an International dealer about having ELC concentrate only to arrive (mid flush) and find out it was 50/50 mix. I pulled my EGR valve cleaned it up real good and the code went away.

Jump to May and 107K miles on the truck and the code started popping up every 10 miles of driving. Finally gave in and took it to the stealership. After of week of back and forth and numerous tests, I was told my manifold was caked with carbon deposits and need to be steam cleaned, and repeatedly reassured my EGR and oil coolers were fine(which is why it took a week, i had them check and recheck). Instead of paying $1500 or so to have them steam clean it, I pulled it cleaned it and put it all back in as well as a new EGR valve(just to be on the safe side).

Since then, all had been well. Then over the weekend, actually the exact moment my truck hit 110K miles, the CEL popped back up with p0401. I pulled my EGR valve to look in the manifold and it is still relatively clean(not spotless, but at least to compared to before I cleaned it). My EOT and ECT have a constant 7-9 degree delta, and never stray from that range. I am not losing coolant. I am not having starting issues. I am not having any smoke out the back. I am on my 3rd EGR valve in less than 20K miles. The onlything I have changed in my truck since cleaning the manifold is the straight pipe exhaust, which was done a couple of thousand miles ago.

So my end question here is, why the heck am I getting this code? What makes the p0401 show up? When I get home tonight, I am going to pull my EGR valve again, and check for moisture, but other than that I am clueless what to look for or where to start. Any direction would be appreciated.

There are only a few things this can be. One being that you installed an egr delete, but you have not (why not?).
Next would be a faulty EGR valve. Since you have replaced that many times, this is out.
Faulty wiring. Maybe...
A plugged EGR cooler. Someone (perhaps the previous owner) did a half-azzed egr delete. They stuck a freeze plug into the exhaust opening in the egr cooler to keep the exhaust out of it, thus blocking the flow to the egr valve. The egr valve has a flow sensor that kicks the code.

Your custom tune is capable of blocking this code......Just have to get in contact with your tune writer and have it added in.

I do not have an EGR delete at this point. I did not see a plug when I pulled everything out to do the manifold, but then again, I didn't take the EGR all the way out and only could see in the side where I replaced the short blue tub. I was clueless about these trucks when I bought, and after learning more and more about them for the past 11 months I have just assumed it would be something I do when my warranty runs out.

Wiring. Any idea where I could start with the wiring? The plug is fully seated on the EGR valve, how would I test that the plug is good?

BTW...I am going with Gearhead after I get this resolved for custom tunes(assuming I still have some extra scratch left)

Get the custom tune and forget the code. It is not hurting anything, except maybe .1 mpg.
The tune will delete the code forever, and is a heck of alot cheaper than chasing your tail for no reason.
Just delete the egr cooler next time you dig into the engine.

On your year truck, the EBP sensor is located on the drivers side of the engine and is attached to a bracket that is attached to the front FICM bracket which in turn is attached to the valve cover (lots of attaching going on here). You can see it under the deags bottle.
The sensor sits on top of a stainless steel tube that runs to the exhaust manifold. Use two wrenches, one on the sensor, one on the tube so you don't twist the tube. Clean the sensor and the tube. Since the tube runs down to the exhaust manifold, you can use tiewire and stick that down the tube. It won't hurt anything. You can also just spray some brakecleaner down the tube as well. Don't use that on the sensor though.

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